diff --git a/uncloud/hack/net.py b/uncloud/hack/net.py
index 30d0c03..f28ab7f 100644
--- a/uncloud/hack/net.py
+++ b/uncloud/hack/net.py
@@ -92,6 +92,8 @@ class DNSRA(object):
 
         if use_sudo:
             self.config['sudo'] = 'sudo '
+        else:
+            self.config['sudo'] = ''
 
         #TODO: remove if not needed
         #self.config['vni_dec'] = vni